1. Field of the Invention
The present invention relates to a control device for a vehicle generator-motor and a control method therefor. The vehicle generator-motor is installed mainly on a vehicle to operate as a motor when starting up an engine and during a torque assistance, and to operate as a generator after the engine is started up.
2. Description of the Related Art
In recent years, in order to increase the fuel efficiency, and to comply with the environmental standard, there have been developed a vehicle that is equipped with a generator-motor, and carries out the so-called idle stop operation, in which an engine is stopped when the vehicle is stationary, and the generator-motor is driven to restart up the engine or carry out a torque assistance when the vehicle starts to move.
The generator-motor used on this type of vehicle needs to be small in size, low in cost, and high in torque, and hence often employs a field winding type of synchronous generator-motor, and carries out drive through rectangular wave power supply (for example, Japanese Patent No. 4493639).
Moreover, when the engine torque assistance is carried out by using the generator-motor, an engine control unit needs to recognize a torque currently output by the generator-motor, and then to carry out cooperative control. As means for recognizing the torque, a method of using an AC power and a conversion efficiency to estimate the torque is proposed (for example, Japanese Patent Application Laid-open No. 2000-50689).
Moreover, a method of detecting a current consumption of the generator-motor, and estimating, based on an average current thereof, a state of charge (SOC) of a battery, and a cruising range is proposed (for example, International Patent WO2005/068245).
However, as described above, the generator-motor used in this application is strongly required to be low in cost. Thus, a current sensor for detecting an input current from a power supply into an inverter device of the generator-motor and a current sensor for detecting an output current from the inverter device to an armature winding of a rotary electric machine are often not provided.
Therefore, the current consumption during the drive cannot be acquired, and the conventionally proposed methods cannot be used for the torque estimation, the battery SOC estimation, and the like.